Pressure-retaining device for fluid-pressure brakes.



No. 766,642. PATENTED AUG. 2, 1904. F. MEBTSHBIMER.

PRESSURE RETAINING DEVICE FOR FLUID PRESSURE BRAKES.

APPLICATION FILED JAN. 2, 1904.

NO MODEL. 2 SHEETS-SHEET 1.

814mm foz 71 lar (Mum Q14 Jad "cana PATENTED AUG. 2, 1904.

I. MERTSHEIMER. PRESSURE RETAINING DEVICE FOR FLUID PRESSURE BRAKES.

APPLICATION FILED JAN. 2. 1904.

2 SHEETS-SHEET 2.

N0 MODEL.

UNITED STATES Patented August 2, 1904.

FREDERICK MERTSHEIMER, OF DENVER, COLORADO.

PRESSURE-RETAINING DEVICE FOR FLUID-PRESSURE BRAKES.

SPECIFICATION forming'part of Letters Patent No. 766,642, dated August2, 1904.

Application filed January 2, 1904.

To aZZ whom, it may concern.-

Be it known that I, FREDERICK MnR'rsuEI- MER, of Denver, county ofDenver, and State of Colorado, have invented a new and usefulImprovement in Pressure-Retaining Devices for Fluid-Pressure Brakes, ofwhich the following is a specification.

This invention has reference to the system of fiuid-pressure-operatedbrakes in which the brakes are actuated by brake-cylinders incontrollable communication with auxiliary reservoirs charged through atrain-pipe from a main source of fluid under pressure; and the inventionhas reference more particularly to the mechanism now commonly used inconnection with systems of this type for retaining a working pressure inthe brake-cylinder after it has been operated to apply brakes, to theend that the brake-cylinder will continue to be operative during therecharging of the auxiliary reservoirs. In the operation of this systemof brakes a definite pressure from the main source of supply ismaintained throughout the train-pipe and auxiliary reservoirs, whichpressure when the brakes are to be applied is relieved, and this action,through the medium of a triple valve situated in the communicationbetween the auxiliary reservoirs and the brake-cylinder, will admitpressure to the brake-cylinder from the auxiliary reservoir, and thispressure acting on the brake-piston will apply the brakes. hen thebrakes are to be released, the previous pressure in the train-pipe isreestablished, which action will by means of the triple valve opencommunication of the brake-cylinder with the atmosphere andsimultaneously recharge the a-uxiliary reservoir.

The mechanism for retaining a working pressure in the brake-cylinderwhile the auxiliary reservoir is being recharged is usually in the formof a valve applied in such manner as to control the exhaust of pressurefrom the brake-cylinder, which valve is of such form and constructionthat it will permit the escape of the fluid from the brake-cylinder onlywhen at a certain predetermined pressure, usually fifteen pounds, theresult being that the valve will retain this pressure in thebrake-cylinder under all conditions, so that Serial No. 187,517. (Nomodel.)

while the auxiliary reservoir is being recharged this retained pressureis available for actuating the brakes for retarding the acceleration ofthe train.

It has been found in practice that under certain conditionsfor instance,light unloaded cars on a uniform moderate d0wngrade a retaining-valveformed to retain apressure of fifteen pounds is sutficient; but thereare conditions encountered which demand a much higher retained pressuresuch, for instance, as heavily-loaded cars on mountain grades. It is notfeasible to employ a single retainingvalve to meet both conditions, forthe pressure retained would be such that under the conditions firstnamed the friction of the brakes on the wheels would be too great andsuch as to cause sliding or skidding. It is necessary, therefore, thatthere be available two different retained pressures; and my inventionconsists, therefore, in combining with a mechanism for retaining apredetermined pressure in the brake-cylinder a device for retaining agreater pressure and suitable connections whereby one or the other ofsaid devices may be brought into action at will.

In the accompanying drawings, Figure 1 is a bottom plan view of a carequipped with an air-brake system and showing how my invention isapplied thereto. Fig. 2 is an end elevation of the same as viewed in thedirection of the arrow in Fig. 1, showing my improved pressure-retainingdevice and its connection with the system. Fig.- 3 is a verticallongitudinal sectional view, on an enlarged scale, of thepressure-retaining devices shown in Fig. 2.

Referring to the drawings, and particularly to Fig. 1, 1 represents atrain-pipe extending throughout the length of the train. 2 represents anauxiliary reservoir, 3 a brakecylinder, and I atriple valve, whichlatter controls communication between the train-pipe and auxiliaryreservoir, between the auxiliary reservoir and brake-cylinder, andbetween the brake-cylinder and external atmosphere, as through port 5.As is well understood by those skilled in the art, a definite pressureis maintained in the train-pipe and auxiliary reservoirs, which pressureon being reduced by the engineer by mechanism under his control acts,through the triple valve, to connect the auxiliary reservoir with thebrake-cylinder and applies the brakes, which latter are 1 released bythe reestablishment of the previous pressure in the train-pipe,whichaction opens the brake-cylinder to the external atmosphere and rechargesthe reservoir. In order to retain a working pressure in thebrake-cylinder, it is usual to connect-With the exhaust-port on thetriple valve,through the medium of a connecting-pipe 6, extended upwardat the end of the car, a pressure-retaining valve 7 such as indicated inFig. 3, the purpose being to retain a predetermined working pressure inthe brake-cylinder, so that while the reservoirs are being recharged thebrakes may still act to retard the acceleration of the train. As shownin Fig. 3, this pressure-retaining valve comprises a casing 8, open tothe atmosphere through port 9 in the bottom of the casing, and havingmounted therein a vertically-movable weighted valve 10, which controls aport 11 in the casing communicating with the exhaust of the triple valvethrough the pipe 6. This valve being weighted so as to retain apressure, say, of fifteen pounds is only lifted to open communicationwith the atmosphere by a higher pressure from the brake-cylinder, sothat when the pressure is reduced to this amount the weighted valveseats itself, closes communication with the outside, and retains thepressure in the brake-cylinder. When it is not desired to retain apressure in the brakecylinder, the valve is cut off from communicationwith the pipe 6 by a cook 12, applied in the pipe 6 and of such formthat it may be turned to close communication between the pipe and valveand open the pipe to the atmosphere through port 13.

The foregoing parts may be of the usual and ordinary construction, andexcept in so far as hereinafter indicated and as combined with myimproved device they form nopart of the present invention.

In carrying out my invention I provide a high-pressure device 1 1 of aform and construction which will retain in the brake-cylinder a greaterpressure than that retained by the valve 7, and I so apply this devicethat one or the other may be used, as desired. This high-pressure devicecomprises a valvecasing 15, within which is'a chamber 16, open to theatmosphere, as at 17, and connected by port 18 through the bottom of thecasing with a branch pipe 19, connected in turn with the pipe 6.

Port 18 is formed at its upper end with a valve-seat 20, against whichis adapted to close a valve 21 on the bottom of a vertically-movableweight 22, mounted in chamber 16, the construction being such that fluidunder pressure in pipe 19 will lift the weight and open the valve, andthus establish communication with the atmosphere only when said pressureexceeds that exerted by the weight. The relation of the weight 22 tothat of the weighted valve 10 is such that the former will act to retaina higher pressure in the brake-cylinder, so that for conditions wherethe low-pressure retaining-valve is not suitable the high-pressure valvemay be employed. These relations of the valves may of course be variedto meet the conditions encountered.

In order that the high-pressure device may act to perform its functionswithout interference fromthe low-pressure valve, I provide in the pipe 6at a point between the connection therewith of the branch pipe 19 andthe low-pressure valve a cut-off 23, preferably in the form of aplug-Valve formed so that it may be turned to cut off communication ofthe pipe 6 with the low-pressure valve, under which conditions theexhaust from the brakecylinder will pass through the branch pipe 19 andacting on the high-pressure valve will find its escape only when it isgreat enough to open the high-pressure valve.

In the operation of the system equipped with my improved device when theconditions are such as to demand the retention only of a light workingpressure in the brake-cylinder plug-valve 23 is opened, so as to allowthe exhaust to pass to the low-pressure-retaining valve, which will actto retain a light working pressure in the brake-cylinder. The fact thatthe high-pressure Valve is also and at all times in communication withthe exhaust of the brake-cylinder will not affect the operation of thelow-pressure valve, for the reason that it operates only at a highpressure. When, on the other hand, the conditions are such as to demandthe retention of the higher working pressure in the brake-cylinder,valve 23 is closed, so as to cut out the low-pressure valve, under whichconditions the exhaust can only find its escape through thehigh-pressure valve when its pressure is such as to operate said valve,and consequently a higher pressure will be retained in thebrake-cylinder.

hen it is not desired to employ either of said pressure-retainingdevices, cut-off cook 12 is turned to close communication between thepipe 6 and the low-pressure valve and open said pipe to the atmospherethrough port 13. In this position of the parts the exhaust will pass tothe atmosphere and will not be obstructed by either of theretainingvalves.

Having thus described my invention, what I claim is 1. In adevice of theclass described the combination with a brake-cylinder of means forsupplying fluid under pressure thereto, a pair of pressure-valves innormal communication with the cylinder and operable independently bydifierent pressures in the latter and means for closing communicationbetween the low-pressure valve and cylinder at will.

2. Inadevice of the class described the combination with abrake-cylinder, of means for IIO said valves being in normalcommunication with and independently operable by different pressures inthe cylinder, and a cut-off valve in the exhaust-duct at a point beyondthe branch duct for closing communication between the low-pressure valveand cylinder at will.

In testimony whereof I hereunto set my hand, this 10th day of December,1903, in the presence of two attesting witnesses.

FREDERICK MERTSHEIMER.

WVitnesses:

WV. B. DUNLEVY, H. A. MAHAN.

